1. Field of the Invention
The subject matter of this invention relates to the preparation of noncellular polyurethanes. It is particularly concerned with the use of certain organo-zirconium and organo-mercury compounds as co-catalysts in the preparation of noncellular polyurethanes.
2. Description of the Prior Art
It is known that polyurethanes are prepared by the reaction of an organic polyisocyanate with an organic compound containing at least two active hydrogen atoms as determined by the Zerewitinoff method. Catalysts are usually used in the preparation of polyurethanes to increase the reaction rate. It is also known that tertiary amines and organo-metallic compounds such as organo-mercury compounds are effective catalysts for the polyurethane reaction.
The prior art also discloses that zirconium alcoholates can be used as catalysts for the preparation of certain polyurethanes. See U.S. Pat. No. 3,673,159. However, the prior art indicates that zirconium tetracetylacetonate and zirconium salts of carboxylic acids are not effective catalysts for the preparation of polyurethanes. See U.S. Pat. No. 3,673,159 and the article by J. W. Britain et al, "Catalysis of the Isocyanate-Hydroxyl Reaction," Journal of Applied Polymer Science, Vol. 4, pages 207-211 (1960).